1. Field of Invention
The invention relates to a sampling circuit for a current transformer.
2. Related Art
With the development of technologies, the current transformer (CT) has been commonly used in various electronic products, such as a power supply, a detector, or a transformer. The current transformer can be roughly divided into an AC-to-DC kind and a DC-to-DC kind according to the transformation method.
In the current technology, the AC-to-DC or DC-to-DC current transformer obtains the current signal by a phase-locked and frequency-locked method. However, when the inputted AC or DC power has an abrupt fluctuation, the current transformer can not operate until the correct phase and frequency is judged. During the idling period, the power still needs to be provided, so the filter capacity needs to be increased. Therefore, the space and cost of the product are both increased.
Besides, the DC-to-DC current transformer normally operates in the first quadrant, and therefore an additional period is necessary for leaking the energy of the current transformer in order to avoid the saturation: Accordingly, the 100% duty cycle can not be reached.
Therefore, it is an important subject to provide a sampling circuit of a current transformer so that the filter capacity needn't be increased when the inputted AC or DC power has an abrupt fluctuation, and thus the space and cost of the product will not be increased, and the 100% duty cycle can be reached.